1. Field of the Invention
The present invention relates to the field of micro-injecting devices and ink jet print heads, particularly to membrane-type micro-injecting devices, and more particularly to the channel arrays for supplying working fluid in the devices.
2. Description of the Prior Art
Micro-injecting devices are able to discharge liquids of a variety of colors by using cartridges. Among the advantages of these devices is low noise. Also, there is an advantage when used in an ink-jet printer that letters printed on paper are fine and clear. As a result, the use of the ink-jet printers has been increasing.
A printer head is mounted in the ink-jet printer. The printer head sprays ink outward after transforming and expanding the ink in a bubble according to electric signals from outside of the printer, thereby carrying out the operation of printing letters on a paper.
Examples of the construction and operation of several ink jet print heads of the conventional art are seen in the following U.S. Patents. U.S. Pat. No. 4,490,728, to Vaught et al., entitled Thermal Ink Jet Printer, describes a basic print head. U.S. Pat. No. 4,809,428, to Aden et al., entitled Thin Film Device For An Ink Jet Printhead and Process For Manufacturing Same and U.S. Pat. No. 5,140,345, to Komuro, entitled Method Of Manufacturing a Substrate For A Liquid Jet Recording Head And Substrate Manufactured By The Method, describe manufacturing methods for ink-jet printheads. U.S. Pat. No. 5,274,400, to Johnson et al., entitled Ink Path Geometry For High Temperature Operation Of Ink-Jet Printheads, describes altering the dimensions of the ink-jet feed channel to provide fluidic drag. U.S. Pat. No. 5,420,627, to Keefe et al, entitled Ink Jet Printhead, shows a particular printhead design.
Generally, these micro injecting devices use high temperature of heat generated by a heating layer within the device to spray the ink on the paper. Accordingly, the high temperature which is generated by the heating layer has an effect on ink contained in an ink chamber for a long time. As a result, the ink is thermally transformed and this causes the durability of the apparatus containing the ink to decrease rapidly.
Recently, to overcome this problem, there has been proposed a new method for smoothly spraying ink from the ink chamber toward the outside by disposing a plate membrane between the heating layer and the ink chamber and inducing a dynamic deformation of the membrane under a pressure of a working fluid, for example, heptane. Since the membrane is disposed between the ink chamber and the heating layer, preventing the ink from contacting directly to the heating layer, the ink itself is subjected to little thermal transformation. An example of this type of printhead is seen in U.S. Pat. No. 4,480,259, to Kruger et al., entitled Ink Jet Printer With Bubble Driven Flexible Membrane.
In ink-jet printer heads of the conventional art using this method, the working fluid, which is supplied into an inlet of the printer head, flows along the main channel for supplying the working fluid, which is defined by means of barrier layers of the heating chamber. Then, the working fluid branches out from the main channel for supplying the working fluid and flows along a feeder channel for supplying the working fluid. At the end of the channel, the working fluid fills up the heating chamber.
The main channel and feeder channel for supplying the working fluid are formed by etching the barrier layer while the heating chamber is formed from the barrier layer. However, when the barrier layer is not etched sufficiently, such that the channel for supplying the working fluid is blocked by the barrier layer of the heating chamber, the working fluid which is introduced into the inlet of the print head cannot flow toward the heating chamber. As a result, the heating chamber is not filled with the working fluid.
Furthermore, when a foreign substance, such as dust or other particle, is introduced into the channel for supplying the working fluid during the process of the etching, thus obstructing a pathway of the working fluid, the working fluid cannot flow toward the heating chamber, as described above. As a result, the heating chamber is not filled with the working fluid.
When the heating chamber is not sufficiently supplied with working fluid because the barrier layer obstructs the pathway of the working fluid, the membrane which is operated by relying on the pressure of the working fluid cannot carry out its function. Accordingly, the printer head does not operate properly.
As described above, the working fluid which is supplied through the inlet of the printer head fills the heating chamber through each channel for supplying the working fluid. As the pressure in the heating chamber is increased by heating from the heating layer, the working fluid introduced into the heating chamber backs up under the pressure and flows along the feeder channel in reverse direction, this backwash resulting in the working fluid being introduced into the adjacent heating chambers. In the case described above, the working fluid is oversupplied for the adjacent heating chambers, while the heating chamber from which the working fluid backwash occurs is subjected to a lack of the working fluid. Therefore, the heating chamber in which the working fluid is oversupplied has a working fluid pressure higher than the desired pressure, while the heating chamber with a lack of the working fluid due to the backwash has a working fluid pressure lower than the desired pressure.
Accordingly, the membranes, which are activated by relying on the pressure of the working fluid, cannot be operated uniformly in their respective heating chambers. The net effect of this phenomenon is that the amount of the ink which is finally sprayed from a respective nozzle is not regular, thereby markedly degrading the quality of printing.